Rear blade angle cylinder bent rod

[Thunder chicken]

So I saw the cylinder on my snowblower chute rotator not being used and thought, why not put it on my 8’ rear blade to have hydraulic angle! It’s a 3” bore cylinder, 1 1/4” rod. (8” stroke).
it worked great until I had it angled (cylinder extended) and caught the inward angled edge. Rod turned into a candy cane!
The blade does not have brackets on it for 2 single acting cylinders. I never looked up to see what the blade should have for a cylinder size, just used what was here!
Would adding a cross over relief on the next cylinder be beneficial? It’s hard to find a 3” cylinder with anything other than a 1 1/4” rod. Anything larger won’t fit without some fabrication work that I’m not going to bother doing. I don’t use the blade often, but not that 1/2 hour that I had angle sure was handy!
I’m pulling this 8’ blade with an M7060.

 

[bcp]

Replace it with the same, but do your work on the other side so it is retracted when angled.

Bruce

 

[Fallon]

A crossover relief wouldn't help. Snow plows have a pair of single acting cylinders fighting each other. So both cylinders have the same cylinder volume. A double acting cylinder has a small er rod end than cylinder end. So if the relief valve on a snow plow opens up the plow angles & an equal amount of fluid moves from one cylinder to the other. On a single cylinder there fluid would need to compress or form a vacuum in order for the cylinder to move.

 

[chim]

With that mounting arrangement the amount of leverage applied to that cylinder by that size of a tractor with a 4' section of the rear blade is kinda like putting a 3 foot cheater bar on a 3/8 drive ratchet wrench.

 

[LD1]

What is the measurement from where the cylinder attaches to the blade king-pin. It looks close. Are you getting full blade angle on both directions with only 8"of stroke? IF so....that is some significant mechanical advantage. hard to know what the tractive force off the tractor is.....but you can kinda figure the force on the cylinder with some basic math.

Say if the cylinder is mounted 6" from the pivot... and you have an 8' blade (4' each direction from the king pin)....you have an 8x mechanical advantage.

So a 3" cylinder at 2500psi is good for 17,600 pounds. With that 8x mechanical advantage of the blade over the cylinder (if indeed its mounted 6" from king pin), all it takes is 2200# of force on the edge of the blade to over-pressure the cylinder. My gut says a m7060 can pull more than that. Was it a shock load....like hitting something hard while going fast....or just brute power?

Although you wont bend a cylinder.....its even worse the other way....when you are angled such that you are trying to EXTEND the cylinder. Anything more than ~1800# of force on the blade edge that is trying to extend the cylinder with the 8x mechanical advantage and you are building MORE than 2500PSI in the cylinder. Again, not likely to bend the rod....but blow a hose and take an oil bath is most likey.

You either need a bigger cylinder, or a longer cylinder with the mounts moved to improve the mechanical advantage.

Did you use existing mounts or something you modified? Were those mounts supposed to be for cylinders? Or something else like turnbuckles? Who made the blade and were cylinders an option? ANd if so, what size?

And Fallon is right, a crossover wont work. Also, If you do it again, use steel hydraulic fittings and ditch the galvanized water pipe stuff.

 

[Thunder chicken]

Thanks for the advice so far
It’s a Farm King blade, 8’. It has a manual adjustment consisting of a bar with holes for pins, you simply choose another hole to adjust the angle.
Chim, the mounts are very close to the king pin. Likely 4-5” at most. I thought about this but had it backward in my mind, that it wouldn’t take much force to move the blade, I didn’t think about it not taking much force to ‘move against’ the cylinder!
Its an older blade so finding what was available for it specifically is likely a wild goose chase but it appears similar blades use a similar sized cylinder but I didn’t look close to see how they were mounted.
I like your idea of maybe changing the mounts, that would require a longer stroke but with less force. As bcp mentioned I could have been working ‘the other way’ but it’s harder to see angled that way and driving down the wrong side of the road, not that it matters.
The cross over relief advice makes sense, thanks for that.
Guess I got some thinking to do, and a few trips in and or if the cab in the meantime to adjust the blade!

 

[Rustyiron]

You guys saying that a x over valve won't work.....that was also my first thought as I've only used one in a typical 2 s.a. cylinders snow plow. But briefly arguing with myself, wouldn't it work between the extend/retract ports as well?
I may be commenting early, but this will be drifting in and out of my thoughts today .

 

[Thunder chicken]

I kinda thought the same Rusty..... then I overcomplicated my thoughts by wondering... if the cylinder is being forced closed, there’d be X oil from the base end going into the rod end. But for it to move say 3” after fetching a big stone, the 3” worth of fluid leaving the base end would put enough fluid in the rod end to move it 4-5”.....? ( took me a few tries to think and write this, boy it’s early somewhere!)
I did find a manual for this blade, and they use a 3.5” bore cylinder, with a 1.5” rod, mounted in the same locations.

I thought I posted this thread in the Hydraulics section! oops

 

[Rustyiron]

I know there's a volume/ displacement issue depending on the direction, but hopefully someone with hydraulic engineering will jump in. Maybe you could simply engineer a little 1/2" bolt into the situation as a shear pin.

 

[5030]

Undersized cylinder (rod diameter) = bent. Time for a stouter cylinder.